1. Field of the Invention
The present invention relates to fiber optic networks, and more particularly to an optical conversion device for a shared FTTH distribution network that enables reliable and cost effective optical communications to the home.
2. Description of the Related Art
Fiber To The Home (FTTH) is an attractive option that has received a significant amount of attention in recent years. Significant technological advances have been made in fiber optic communications. FTTH promises to deliver “true” broadband access compared to existing access technologies including network connections based on phone lines (DSL) or coaxial cable. The hybrid-fiber-coax (HFC) architecture is a relatively recent development adopted by the cable industry in which optical signals are transported from a source of distribution (e.g., a headend) to multiple electro-optical conversion nodes via fiber optic cables. Each conversion node converts between optical signals and electrical signals using simple photo-detector technology, where the electrical signals are carried via coaxial cables routed from the conversion nodes to individual subscriber locations. Each subscriber location is typically a residential location (e.g., home, duplex, apartment building, etc.) or a business location or the like, where each subscriber location supports one or more individual subscribers. Current HFC designs call for fiber nodes serving about 500 homes on the average, although the nodes could be further segmented to smaller coaxial-serving areas.
A “last mile” solution to achieve FTTH would appear to be to replace the coax cables of an HFC architecture with fiber optic cables. The traditional Passive Optical Network (PON) approach to FTTH is to route a separate optical fiber to each subscriber location. Such a solution, however, results in about 1,000 fibers on the average between each local node and the neighborhoods served (2 per house for full duplex). The average number of fibers behind each person's home in such a configuration is about 200. This has proved to be an unwieldy architecture that is difficult to establish and prohibitively expensive to maintain. FTTH has not yet proved to be cost effective to deploy and/or operate using conventional approaches.
Experience from the coaxial cable configurations has demonstrated that cable problems can and do occur. Generally, damage to one or more cables reduces or otherwise eliminates service in corresponding downstream geographic areas. Coaxial cables are relatively inexpensive and easy to replace and/or repair. Fiber optic cables, on the other hand, are relatively expensive and difficult to repair. In proposed configurations, each cable has a multitude of optical fibers. During the installation process, the individual fibers must be identified and isolated to route each fiber to the appropriate location. Fiber optic cable repair has typically required very specialized equipment involving a sophisticated splicing operation that must be done in a relatively clean environment. The solution has been a truck or “splicing van” loaded with very expensive fiber optic splicing equipment. The general process is to clean, align and splice, which involves melting and firing the individual fibers. The splicing van must be deployed to the specific trouble spot in the network. Although access may be readily available at or near major thoroughfares, such as highways or rural access routes where van access is readily available, such access is more problematic behind homes in neighborhoods and many other hard to reach or remote locations.
It is desired to solve the last mile dilemma so that FTTH can become a viable and economic reality.